Differences between Innate and Acquired (Adaptive) Immunity

Immunity is defined as the resistance offered by the host against microorganism(s) or any other foreign substance(s). Immunity can be broadly classified into two types:

  • Innate Immunity-present right from the birth
  • Acquired/Adaptive Immunity- acquired during the course of the life.

The innate immune system recognizes molecular structures that are unique to microbes called pathogen associated molecular patterns (PAMPs) via pattern recognition receptors (PRR). The innate immune system aims to eliminate microbes and other foreign particles using:

  1. Physical barriers
  2. Proteins (complement)
  3. Cells (phagocytosis, cytotoxic killing).

But many pathogens can breach/resist innate immune system. To clear such pathogens specific and more robust adaptive immunity comes into play. There are two types of adaptive immune response, humoral immunity (where products of B-cells (precisely plasma cells) i.e. antibodies bind with specific extracellular antigens and cells mediated immunity, whereas T cells (precisely Cytotoxic T Cells)  kills both intracellular antigen and altered self cells. T helper cells help in the humoral immunity.

Some of the major differences between Innate Immunity and Adaptive Immunity is summarized in the table below (To give different perspectives, i have made this table bit lengthy, some properties may look similar thus can be grouped in your convenience):

Innate Immunity Adaptive/Acquired  Immunity
Definition Innate immunity is the inborn resistance against infections that an individual possesses right from the birth, due to his genetic or constitutional markup. Acquired immunity is the resistance against infecting foreign substance that an individual acquires or adapts during the course of life.
Origin Prior exposure to the antigen is not required. It is present before the first exposure to microbial antigen. Develops during lifetime  following the antigenic exposure
Activity Always present Normally silent but triggers often exposure to pathogens
Diversity Diversity is limited; It is active only against a limited repertoire of antigens. Adaptive immunity is more varied and involves specialized immune responses.
Specificity Non-specific, defends against any pathogen up on first exposure Antigen specific-responds to specific pathogen on 2nd or latter exposure
Functional against General microbes (bacteria, fungi, parasites) etc, Chemical irritants, burns, tissue injury etc. Microbes as well as non microbial substance called antigen
Response time Immune response occurs in minutes Takes days to generate immune response
Potency It  has a limited and lower potency It has highly potent  immune response
Target  Antigens Innate immunity develops against antigens that are shared by many microbes (called pathogens-associated molecular patterns). Acquired immunity develops against antigens that are specific for each microbe.
Host Cell Receptors Host cell receptors of innate immunity (called pattern recognition receptors) are non-specific, e.g. Toll-like receptor Host cell receptors are specific, e.g. T cell receptor and B cell immunoglobulin receptor.
Immunological Memory

Absent

It reacts with equal potency upon repeated exposure to same pathogen.

Present
Presence of memory cells triggers a faster and potent response when re-exposed to same pathogens.
Heritance Innate immunity is inheritable Passive acquired immunity is heritable from mother to neonates for a brief period after birth.
Components
  • Anatomical /physiological barrier like skin, mucous membrane, temperature, pH, Chemicals Cells-
  • Phagocytes (Monocytes, Macrophages, Neutrophils), Natural killer cells
  • Complement (Alternative & MBL Pathway),
  • Normal resident flora etc.

 

  • T Cell
  • B Cell
  • Classical complement pathway
  • Antigen presenting cells
  • Cytokines etc.

 

About tankeshwar 367 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion, I am working as a Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.

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